System and method for tracking eyeball motion

ABSTRACT

Detecting position information related to a face, and more particularly to an eyeball in a face, using a detection and ranging system, such as a Radio Detection And Ranging (“RADAR”) system, or a Light Detection And Ranging (“LIDAR”) system. The position information may include a location of the eyeball, translational motion information related to the eyeball (e.g., displacement, velocity, acceleration, jerk, etc.), rotational motion information related to the eyeball (e.g., rotational displacement, rotational velocity, rotational acceleration, etc.) as the eyeball rotates within its socket.

RELATED APPLICATIONS

The present application is a continuation of application Ser. No.13/470,715, which was filed on May 14, 2012, now U.S. Pat. No. ______;which in turn is a continuation of application Ser. No. 12/762,772,which was filed on Apr. 19, 2010, now U.S. Pat. No. 8,177,363; which inturn is a continuation of application Ser. No. 11/610,867, which wasfiled on Dec. 14, 2006, now U.S. Pat. No. 7,699,469; and claims priorityfrom U.S. Provisional Patent Application No. 60/750,045, entitled“System and Method for Tracking Eyeball Motion,” filed Dec. 14, 2005.The contents of these applications are incorporated herein by reference.This application is related to U.S. Provisional Patent Application No.60/651,989, entitled “Chirped Coherent Laser Radar System and Method,”filed Feb. 14, 2005, the contents of which are also incorporated hereinby reference.

FIELD OF THE INVENTION

The invention relates generally to tracking the movement of an eyeball,and more particularly to tracking the movement of an eyeball using adetection and ranging system.

BACKGROUND OF THE INVENTION

Determining the motion of an eyeball of an individual may have practicalapplication in a multitude of environments. For example, eyeball motionmay be monitored in iris and/or corneal recognition systems, stimulusresponse measurement, medical procedures, virtual reality systems, orother environments. Eyeball motion information may enable improvedimaging of the eyeball, iris or retinal. Eyeball motion information mayalso enable imaging of the eyeball, iris, or cornea at greater rangesthan would otherwise be possible.

However, conventional eyeball motion tracking systems, such as stereosystems, may not provide position information related to an eyeball withenough speed and/or accuracy for all of the possible applications ofeyeball motion tracking. In general, these systems may also be hamperedby an inability to determine position information related to an eyeballfrom a relatively extended distance.

These and other drawbacks associated with conventional eyeball motiontracking systems and methods exist.

SUMMARY

One aspect of the invention relates to detecting position informationrelated to a face, and more particularly to an eyeball in a face, usinga detection and ranging system, such as a Radio Detection And Ranging(“RADAR”) system, or a Light Detection And Ranging (“LIDAR”) system. Theposition information may include a location of the eyeball,translational motion information related to the eyeball (e.g.,displacement, velocity, acceleration, jerk, etc.), rotational motioninformation related to the eyeball (e.g., rotational displacement,rotational velocity, rotational acceleration, etc.) as the eyeballrotates within its socket. One of the advantages of the implementationof a detection and ranging system in detecting position informationrelated to the eyeball may include an increased speed at which theposition information may be determined. In fact, in someimplementations, the determination of the position information may besubstantially instantaneous with substantially no latency. Anotheradvantage of the implementation of a detection and ranging system indetecting position information related to the eyeball may includeenabling eyeball motion to be determined from an increased distanceand/or with a reduced invasiveness to the individual.

As mentioned above, the detection and ranging system may include acoherent LIDAR system. In these implementations, a first set ofelectromagnetic radiation beams may be incident on the eyeball at one ormore locations on the eyeball. The first set of electromagneticradiation beams may be returned from these locations on the eyeball tothe LIDAR system (e.g., via backscattering, reflection, etc.), and thefrequency shift of the returned electromagnetic radiation may bemeasured.

The coherent LIDAR system may determine information related to one orboth of location (e.g., x, y, z) and rotational velocity (e.g., acomponent of the velocity of the surface of the eyeball that is parallelto an incident electromagnetic radiation beam) at each measurementlocation on the eyeball. If the radius of the eyeball is known, thisinformation may be determined with three measurement beams focused onthree separate measurement locations on the eyeball. If the radius isunknown, the radius may be determined with a fourth measurement beamfocused on a fourth separate measurement location on the eyeball. Oncethe eye has been located (e.g., with three measurement beams if theradius is known or with four measurement beams if the radius is notknown), the center of the eye and the closest point of the eye may bedetermined based on the known location.

At individual ones of the measurement locations, a velocity vectorrepresentative of the movement of the eyeball within the eye socket thatis tangential to the surface of the eyeball may be determined. If avalid determination of this velocity vector is made for at least twomeasurement locations on the eyeball that are (i) not the closest pointand are (ii) not on the same great circle with each other and theclosest point, then the rotational motion of the eyeball within itssocket may be determined by the LIDAR system. This may enable thetracking of the lateral rotational motion of the eyeball, and byextension the surface features on the eyeball (e.g., the iris, thepupil, etc.). It should be appreciated that the eyeball may not beformed as a perfect sphere, and that asymmetries in the shape of theeyeball may impact the velocity vector that is calculated at a givenmeasurement location on the eyeball. However, eyeball shape in generalis close enough to spherical that typically any non-uniformities in theeyeball may be de minimis and, as such, the eyeball may assumed to beperfectly spherical in some embodiments (and for illustrative purposesherein).

In some implementations, lateral or vertical motion of the face thatdisplaces the eye socket, along with the eyeball, may be determined byvideo optical flow processing of video footage captured by a videoimaging system being used in conjunction with the LIDAR system. Rotationin the plane of the image of the video imaging system may also bedetermined in this manner. Movement (e.g., displacement, rotation, etc.)of the face out of the plane of the images captured by the video imagingsystem may be determined by the LIDAR system. For example, a second setof electromagnetic beams may be emitted from the LIDAR system to one ormore locations on the face (other than the eyeball), and range and rangerate measurements of the one or more locations on the face may be madeto determine information related to the movement of the face out of theplane of the images captured by the video imaging system.

The relatively low frequency of head motion and the great number ofmeasurements will allow for a relatively high accuracy of head motiondetermination in this, or some other, manner. This being done, thelocation and velocity of the 3D center points of the eyeballs may bedetermined so that the residual motion of the eyeballs in the eyesockets may be determined separate from the motion of the eye sockets,as if the eyeball were in a stationary socket.

Another aspect of various embodiments of the invention may relate to alaser radar system that unambiguously detects a range of a target and arange rate at which the target is moving relative to the laser radarsystem. Another aspect of various embodiments of the invention mayrelate to a laser radar system that uses multiple laser radar sectionsto obtain multiple simultaneous measurements (or substantially so),whereby both range and range rate can be determined without varioustemporal effects introduced by systems employing single laser sectionstaking sequential measurements. In addition, other aspects of variousembodiments of the invention may enable faster determination of therange and rate of the target, a more accurate determination of the rangeand rate of the target, and/or may provide other advantages.

In some embodiments of the invention, the laser radar system may emit afirst target beam and a second target beam toward a target. The firsttarget beam and the second target beam may be reflected by the targetback toward the laser radar system. The laser radar system may receivethe reflected first target beam and second target beam, and maydetermine at least one of a range of the target from the laser radarsystem, and a range rate of the target. In some embodiments of theinvention, the laser radar system may include a first laser radarsection, a second laser radar section, and a processor.

In some embodiments of the invention, the first laser radar section maygenerate a first target beam and a first reference beam. The firsttarget beam and the first reference beam may be generated by a firstlaser source at a first frequency that may be modulated at a first chirprate. The first target beam may be directed toward a measurement pointon the target. The first laser radar section may combine one portion ofthe first target beam that may be directed towards, and reflected from,the target. Another portion of the first target beam, referred to as alocal oscillator beam, may be directed over a path with a known orotherwise fixed path length. This may result in a combined first targetbeam.

According to various embodiments of the invention, the second laserradar section may be collocated and fixed with respect to the firstlaser radar section. More particularly, the relevant optical componentsfor transmitting and receiving the respective laser beams are collocatedand fixed. The second laser radar section may generate a second targetbeam and a second reference beam. The second target beam and the secondreference beam may be generated by a second laser source at a secondfrequency that may be modulated at a second chirp rate. The second chirprate may be different from the first chirp rate. This may facilitate oneor more aspects of downstream processing, such as, signaldiscrimination, or other aspects of downstream processing. The secondtarget beam may be directed toward the same measurement point on thetarget as the first target beam. The second laser radar section maycombine one portion of the second target beam that may be directedtowards, and reflected from, the target, and another portion of thesecond target beam that may be directed over a path with a known orotherwise fixed path length. This results in a combined second targetbeam.

According to various embodiments of the invention, the processorreceives the first and second combined target beams and measures a beatfrequency caused by a difference in path length between each of therespective reflected target beams and its corresponding local oscillatorbeam, and by any Doppler frequency shift created by target motionrelative to the laser radar system. The beat frequencies may then becombined linearly to generate unambiguous determinations of the rangeand the range rate of the target, so long as the beat frequenciesbetween each of the respective local oscillator beams and the itsreflected target beam correspond to simultaneous (or substantiallysimultaneous) temporal components of the reflected target beams.Simultaneous (or substantially simultaneous) temporal components of thereflected target beams may include temporal components of the targetbeams that: 1) have been incident on substantially the same portion ofthe target, 2) have been impacted by similar transmission effects, 3)have been directed by a scanning optical element under substantially thesame conditions, and/or 4) share other similarities. The utilization ofbeat frequencies that correspond to simultaneous (or substantiallysimultaneous) temporal components of the reflected target beams forlinear combination may effectively cancel any noise introduced into thedata by environmental or other effects.

Because the combined target beams may be created by separately combiningthe first local oscillator beam and the second local oscillator beamwith different target beams, or different portions of the same targetbeam, the first combined target beam and the second combined target beammay represent optical signals that might be present in two separate, butcoincident, single source frequency modulated laser radar systems, justprior to final processing. For example, the combined target beams mayrepresent optical signals produced by target interferometers in thesingle source systems.

According to various embodiments, the target beams may be directed toand/or received from the target on separate optical paths. In someembodiments, these optical paths may be similar but distinct. In otherembodiments the first target beam and the second target beam may becoupled prior to emission to create a combined target beam that may bedirected toward the target along a common optical path. In someembodiments, the target beam may be reflected by the target and may bereceived by the laser radar system along a reception optical pathseparate from the common optical path that directed the target beamtoward the target. Such embodiments may be labeled “bistatic.” Or, thecombined target beam may be received by the laser radar system along thecommon optical path. These latter embodiments may be labeled“monostatic.” Monostatic embodiments may provide advantages over theirbistatic counterparts when operating with reciprocal optics. Moreparticularly, monostatic embodiments of the invention are less affectedby differential Doppler effects and distortion due to speckle, amongother things. Differential Doppler effects are created, for example, bya scanning mirror that directs the target beam to different locations ona target. Since different parts of the mirror are moving at differentvelocities, different parts of the target beam experience differentDoppler shifts, which may introduce errors into the range and or rangerate measurements. These effects have been investigated and analyzed byAnthony Slotwinski and others, for example, in NASA Langley Contract No.NAS1-18890 (May 1991) Phase II Final Report, Appendix K, submitted byDigital Signal Corporation, 8003 Forbes Place, Springfield, Va. 22131,which is incorporated herein by reference in its entirety.

In some instances, the first laser source and the second laser sourcemay generate electromagnetic radiation at a first carrier frequency anda second carrier frequency, respectively. The first carrier frequencymay be substantially the same as the second carrier frequency. This mayprovide various enhancements to the laser radar system, such as, forexample, minimizing distortion due to speckle, or other enhancements.

In some embodiments, the first laser source and the second laser sourcemay provide electromagnetic radiation with highly linearized frequencychirp. To this end, the linearization of the electromagnetic radiationemitted by the first laser source and the second laser source may becalibrated on a frequent basis (e.g. each chirp), or in some embodimentscontinuously (or substantially so). This linearization the frequencychirp of the electromagnetic radiation may provide enhanced rangemeasurement accuracy, or other enhancements, over conventional systemsin which linearization may occur at startup, when an operator noticesdegraded system performance, when the operator is prompted to initiatelinearization based on a potential for degraded performance, or when oneor more system parameters fall out of tolerance, etc. Frequent and/orautomated linearization may reduce mirror differential Doppler noiseeffects during high speed scanning and may maximize the effectiveness ofdual chirp techniques for canceling out these and other noisecontributions to range estimates.

In some embodiments of the invention, the laser radar system maydetermine the range and the range rate of the target with an increasedaccuracy when the range of the target from the laser radar system fallswithin a set of ranges between a minimum range and a maximum range. Whenthe range of the target does not fall within the set of ranges, theaccuracy of the laser radar system may be degraded. This degradation maybe a result of the coherence length(s) of the first laser source and thesecond laser source, which is finite in nature. For example, thedistance between the minimum range and the maximum range may be afunction of the coherence length. The longer the coherence length of thefirst laser source and the second laser source, the greater the distancebetween the minimum range and the maximum range. Thus, increasing thecoherence length of the first laser source and the second laser sourcemay enhance range and range rate determinations by the laser radarsystem by providing the ability to make determinations over an enhancedset of ranges.

In some embodiments of the invention, one or both of the first lasersource and the second laser source may implement a system and method forcontrollably chirping electromagnetic radiation from a radiation source.The system and method may enable electromagnetic radiation to beproduced at a substantially linear chirp rate with a configurableperiod. In some embodiments, the radiation may include a single,frequency shifted, resonant mode.

In some embodiments of the invention, a system may include a radiationsource, one or more optical elements that form an optical cavity, afrequency shifter, an optical switch and an optical amplifier. In someembodiments, the frequency shifter may be disposed within the opticalcavity to receive electromagnetic radiation from the optical cavity, andto output a frequency shifted portion of the received electromagneticradiation back to the optical cavity. The optical switch may be disposedwithin the optical cavity to receive electromagnetic radiation from theoptical cavity. The optical switch may be controllable to either directthe received electromagnetic radiation away from the optical cavity, orto return the received electromagnetic radiation back to the opticalcavity. In some instances, the optical switch may be controllable tocouple radiation from the radiation source to the optical cavity whiledirecting the received electromagnetic radiation away from the opticalcavity, the radiation from the source being received at the opticalswitch at an initial frequency.

According to various embodiments of the invention, the optical cavitymay be “filled” by directing radiation from the laser source, emitted atthe initial frequency, into the optical cavity for a period of time thatcorresponds to the optical length of the optical cavity. In someembodiments, the radiation from the laser source may be directed intothe optical cavity by the optical switch. While the electromagneticradiation from the laser source is being directed in to the cavity, theoptical switch may be controlled to direct radiation received by theoptical switch away from the optical cavity, or “dumped” from thecavity. Once the cavity is “filled” (e.g., after the time periodcorresponding to the optical length of the optical cavity has passed)the flow of radiation from the laser source to the optical cavity may behalted. In some embodiment, the flow of radiation from the laser sourceto the optical cavity may be halted by powering down the laser source.In other embodiments, the flow of radiation from the laser source to theoptical cavity may be halted by controlling the optical switch to dumpthe radiation from the laser source away from the optical cavity. Theradiation injected into the optical cavity while the cavity was beingfilled, may be circulated within the cavity by the optical switch, whichmay be controlled to direct radiation received from the optical cavityback into the optical cavity.

In some embodiments of the invention, as the electromagnetic radiationis circulated within the optical cavity, the frequency of the radiationmay be incrementally adjusted by the frequency shifter during each triparound the optical cavity. Through this periodic, incrementaladjustment, the frequency of the radiation within the optical cavity maybe chirped in a substantially linear manner. The rate at which thefrequency of the electromagnetic radiation is chirped may be related toone or both of the incremental frequency adjustment applied by thefrequency shifter and the optical length of the cavity. Thus, the rateat which the frequency of the radiation is chirped, may be controlledvia one or both of these variables.

In some embodiments, a quality factor of the optical cavity may bedegraded by various losses within the optical cavity. For example,radiation output from the optical cavity to a device may constitute aloss. Other losses may also be present, such as losses due toimperfections in the optical elements, or other parasitic losses. Tocombat the degradation of the quality factor, an optical amplifier maybe disposed within the optical cavity. The optical amplifier may beselected or controlled to provide enough gain to radiation within theoptical cavity to overcome the sum of the cavity losses so that apredetermined or controlled intensity of radiation output from theoptical cavity may be maintained. The optical amplifier may also beselected based on one or more other characteristics, such as, forexample, homogeneous line width, gain bandwidth, or otherspecifications.

In some embodiments of the invention, one of the chirp rates may be setequal to zero. In other words, one of the laser sources may emitradiation at a constant frequency. This may enable the laser sourceemitting at a constant frequency to be implemented with a simplerdesign, a small footprint, a lighter weight, a decreased cost, or otherenhancements that may provide advantages to the overall system. In theseembodiments, the laser radar section with chirp rate set equal to zeromay be used to determine only the range rate of the target.

In some embodiments of the invention, the processor may linearly combinethe first combined target beam and the second combined target beamdigitally to generate the range signal and the range rate signal. Forexample, the processor may include a first detector and a seconddetector. The first detector may receive the first combined target beamand may generate a first analog signal that corresponds to the firstcombined target beam. The first analog signal may be converted to afirst digital signal by a first converter. The processor may include afirst frequency data module that may determine a first set of frequencydata that corresponds to one or more frequency components of the firstdigital signal.

The second detector may receive the second combined target beam and maygenerate a second analog signal that corresponds to the second combinedtarget beam. The second analog signal may be converted to a seconddigital signal by a second converter. The processor may include a secondfrequency data module that may determine a second set of frequency datathat corresponds to one or more of frequency components of the seconddigital signal.

The first set of frequency data and the second set of frequency data maybe received by a frequency data combination module. The frequency datacombination module may generate a range rate signal and a range signalderived from the first set of frequency data and the second set offrequency data.

In other embodiments of the invention, the processor may mix the firstcombined target beam and the second combined target beam electronicallyto generate the range signal and the range rate signal. For example, theprocessor may include a modulator. The modulator may multiply the firstanalog signal generated by the first detector and the second analogsignal generated by the second detector to create a combined analogsignal. In such embodiments, the processor may include a first filterand a second filter that receive the combined analog signal. The firstfilter may filter the combined analog signal to generate a firstfiltered signal. The first filtered signal may be converted by a firstconverter to generate a range rate signal. The second filter may filterthe combined analog signal to generate a second filtered signal. Thesecond filtered signal may be converted by a second converter togenerate a range signal.

According to other embodiments of the invention, the processor may mixthe first combined target beam and the second combined target beamoptically to generate the range signal and the range rate signal. Forexample, the processor may include a detector that receives the firstcombined target beam and the second combined target beam and generates acombined analog signal based on the detection of the first combinedtarget beam and the second combined target beam. In such embodiments,the processor may include a first filter and a second filter thatreceive the combined analog signal. The first filter may filter thecombined analog signal to generate a first filtered signal. The firstfiltered signal may be converted by a first converter to generate arange rate signal. The second filter may filter the combined analogsignal to generate a second filtered signal. The second filtered signalmay be converted by a second converter to generate a range signal.

These and other objects, features, and characteristics of the presentinvention, as well as the methods of operation and functions of therelated elements of structure and the combination of parts and economiesof manufacture, will become more apparent upon consideration of thefollowing description and the appended claims with reference to theaccompanying drawings, all of which form a part of this specification,wherein like reference numerals designate corresponding parts in thevarious figures. It is to be expressly understood, however, that thedrawings are for the purpose of illustration and description only andare not intended as a definition of the limits of the invention. As usedin the specification and in the claims, the singular form of “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a system for monitoring motion of an eyeball of anindividual according to one or more embodiments of the invention.

FIG. 2 illustrates a laser radar system that may be implemented in thesystem for monitoring an eyeball of an individual according to one ormore embodiments of the invention.

FIG. 3 illustrates a laser radar system that may be implemented in thesystem for monitoring an eyeball of individual according to one or moreembodiments of the invention.

FIG. 4 illustrates a processor that digitally mixes two combined targetbeams according to one or more embodiments of the invention.

FIG. 5 illustrates a processor that electrically mixes two combinedtarget beams according to one or more embodiments of the invention.

FIG. 6 illustrates a processor that optically mixes two combined targetbeams according to one or more embodiments of the invention.

DETAILED DESCRIPTION

FIG. 1 is an exemplary illustration of a system 110 for detectingposition information related to a face, and more particularly to aneyeball in a face of an individual 112, in accordance with someembodiments of the invention. System 110 may determine positioninformation related to the eyeball of individual 112. System 110 mayinclude a laser radar system 116 capable of determining a range toand/or a range rate (i.e., velocity) of a point on a surface ofindividual 112 (e.g., skin, clothing, lips, etc.). System 110 mayinclude a monitor module 118 capable of determining position informationrelated to the eyeball of individual 112 based on the determinations oflaser radar system 116. System 110 may enable the position informationrelated to the eyeball of individual 112 to be monitored and determinedremotely from individual 112 without directly contacting individual 112.

In some embodiments of the invention, laser radar system 116 may directa beam of electromagnetic radiation 114 toward individual 112 to beincident on individual 112 at a point on the surface of individual 112to be measured. Some or all of radiation 114 directed to the point onthe surface of individual 112 may be reflected by the surface, and maythen be received back into laser radar system 116. As described below,based on one or more aspects of radiation 114 (e.g., frequency, phase,intensity, etc.) prior to emission and/or subsequent to reflection,laser radar system 116 may determine one or both of the range and therange rate of the point on the surface with respect to laser radarsystem 116.

According to various embodiments of the invention, laser radar system116 may make a plurality of determinations of range and/or range rate ofa set of measurement points on a surface of the eyeball of individual112 (e.g., at a periodic rate) over a period of time. Monitor module 118may implement the determined ranges and range rates to determine theposition information related to the eyeball.

According to various embodiments of the invention, monitor module 118may additionally monitor movement of the head of individual 112, inorder to more accurately determine position information related to theeyeball of individual 112. In some of these embodiments, system 110 mayinclude a video imaging system that captured video footage (successiveimages) of individual 112. Lateral or vertical motion of the face ofindividual 112 (in the plane of the images captured by the video imagingsystem) that displaces the eye socket, along with the eyeball, may bedetermined by video optical flow processing (or some other motiontracking processing) of the video footage captured by the video imagingsystem. Similarly, the rotation of the face of individual 112 within theimage plane may be determined. In this way, three degrees of motion maybe measured by the video imaging system. This optical flow processingmay be performed by monitor module 118. Motion of the face of individual112 out of the plane of the images captured by the video imaging systemmay be determined by taking measurements of the face (outside of the eyesockets) by laser radar system 116. These motions comprise range motion(a translational degree of freedom) and the two rotational degrees offreedom that are orthogonal to the image plane of the video imagingsystem. Thus, by combining the information determined from the videofootage captured by the video imaging system and the measurements oflaser radar system 116, monitor module 118 may determine the motion ofthe face of individual 112 in six degrees of freedom.

By determining the motion of the face of individual 112, monitor module118 may track the motion and/or position of the eye socket of individual112. Monitor module 118 may adjust determinations of the position and/ormovement of the eyeball of individual 112, using the motion and/orposition of the eye socket of individual 112, to reflect only (orsubstantially only) the rotation of the eyeball in the eye socket.

FIG. 2 illustrates a frequency modulated laser radar system 210 that maybe implemented within system 110 as laser radar system 116, according tosome embodiments of the invention. System 210 may include a laser source212 that emits a beam 214 of electromagnetic radiation. Beam 214 may beemitted at a frequency that is continuously varied, or chirped. In someinstances, chirping the frequency may include sweeping the frequencybetween a lower frequency and an upper frequency (or vice versa) in aperiodic manner (e.g. a sawtooth waveform, a triangle waveform, etc.).Beam 214 may be divided by an optical coupler 216 into a target beam 218and a reference beam 220. It should be appreciated that although laserradar system 210 is shown and described as a single beam system, that inorder to provide beams of electromagnetic radiation to a plurality ofpoints on the eyeball of the individual beam 214 may be divided into aplurality of beams, and each beam may then be subsequently processed inthe manner described below.

In conventional embodiments, system 210 may include a targetinterferometer 222 and a reference interferometer 224. Targetinterferometer 222 may receive target beam 218, and may divide thetarget beam at an optical coupler 226. Target interferometer 222 istypically used to generate a target signal that may depend upon a rangeof a target 230 (e.g. individual 112) from target interferometer 222.Target interferometer may accomplish this by directing one portion 228of target beam 218 toward target 230, and the other portion 232 oftarget beam 218 to a target frequency difference module 234 over anoptical path with a fixed path length. Portion 228 of target beam 218may be reflected by target 230 and may be transmitted to targetfrequency difference module 234 via optical coupler 226 and an opticalfiber 236. Based on interference between portions 236 and 232 at coupler248, target frequency difference module 234 may generate the targetsignal corresponding to a beat frequency of portions 236 and 232 oftarget beam 218 due to the difference between their path lengths.

According to various embodiments of the invention, referenceinterferometer 224 may receive reference beam 220 and may generate areference signal corresponding to a frequency difference between twoportions of reference beam 224 that may be directed over two separatefixed paths with a known path length difference. More particularly,reference beam 220 may be divided by an optical coupler 240 into a firstportion 242 and a second portion 244. First portion 242 may have a fixedoptical path length difference relative to second portion 244. Based oninterference between portions 242 and 244 at coupler 246, referencefrequency difference module 250 may generate the reference signalcorresponding to a beat frequency of portions 242 and 244 of referencebeam 220 caused by the fixed difference between their path lengths.

As will be appreciated, target interferometer 222 and referenceinterferometer 224 have been illustrated and described as Mach-Zehnderinterferometers. However other interferometer configurations may beutilized. For example, target interferometer 222 and referenceinterferometer 224 may include embodiments wherein Michelson-Morleyinterferometers may be formed.

In some embodiments, system 210 may include a processor 238. Processor238 may receive the target signal and the reference signal and mayprocess these signals to determine the range of target 230. Rangeinformation determined based on the target signal and the referencesignal may be used to determine a range rate of target 230 with respectto target interferometer 222.

FIG. 3 illustrates an exemplary embodiment of a laser radar system 310that may be implemented within system 110, as laser radar system 116, tomonitor one or more points on a surface of the eyeball of individual112, according to some embodiments of the invention. Laser radar system310 may employ two or more laser radar sections, each of which emits atarget beam of radiation toward a target. For example, a first laserradar section 374 emits a first target beam 312 and a second laser radarsection 376 emits a second target beam 314 toward a target 316 (e.g.,individual 112). In some embodiments of the invention, first target beam312 and second target beam 314 may be chirped to create a dual chirpsystem. The implementation of laser radar system 310 in system 110 tomonitor one or more points on a surface of the eyeball of individual 112may provide unambiguous determinations of the range and the range rateof the points on the surface of the eyeball of individual 112 withrespect to system 110, and may enable enhanced determinations ofposition information related to the eyeball of individual 112 bymonitoring module 118. For example, the unambiguous determination of therange and/or the range rate of the points on the surface of the eyeballof individual 112 may reduce an amount of noise in the determined rangesand/or range rates. If present, the noise may impact the accuracy of thedeterminations of the ranges and/or range rates. Inaccuracies within thedetermined ranges and/or range rates may hamper determinations thatleverage the determined ranges and/or range rates to positioninformation related to the eyeball of individual 112.

It should be appreciated that although laser radar system 310 is shownand described as a dual beam system that provides two beams incident ona single point, that this description is not limiting and that in orderto provide monitor a plurality of points on the eyeball each of thetarget beams may be divided into a plurality of beams, and each beam maythen be subsequently processed in the manner described below. In someimplementations, the plurality of points on the eyeball may be monitoredby successively by the single point radiation (e.g., by scanning thesingle point of radiation to each of the plurality of points on theeyeball in succession). Although in these implementations the points onthe eyeball may not be monitored absolutely simultaneously, the singlepoint radiation may be provided to each of the plurality of points onthe eyeball quickly enough that the resulting collection of data may beprocessed as if the plurality of points had been monitoredsimultaneously. In some implementations, a hybrid approach may beimplemented in which the beams provided by laser radar system 310 as asingle point of radiation may be divided to provide a plurality ofpoints of radiation, and each of the plurality of points of radiationmay be scanned successively to different points on the eyeball (and/orindividual 112).

According to various embodiments of the invention, laser section 374 mayinclude a laser source controller 336, a first laser source 318, a firstoptical coupler 322, a first beam delay 344, a first local oscillatoroptical coupler 330, and/or other components. Second laser radar section376 may include a laser source controller 338, a second laser source320, a second optical coupler 324, a second beam delay 350, a secondlocal oscillator optical coupler 332 and/or other components. Forexample, some or all of the components of each of laser radar sections374 and 376 may be obtained as a coherent laser radar system from MetrisUSA. Coherent laser radar systems from Metris USA may provide variousadvantages, such as enhanced linearity functionality, enhanced phasewandering correction, and other advantages to laser radar system 310 indetermining the range and the range rate of target 316.

In some embodiments of the invention, first target beam 312 and secondtarget beam 314 may be reflected by target 316 back toward laser radarsystem 310. Laser radar system 310 may receive first target beam 312 andsecond target beam 314, and may determine at least one of a range oftarget 316 from laser radar system 310, and a range rate of target 316.

According to various embodiments of the invention, first laser source318 may have a first carrier frequency. First laser source 318 may emita first laser beam 340 at a first frequency. The first frequency may bemodulated at a first chirp rate. The first frequency may be modulatedelectrically, mechanically, acousto-optically, or otherwise modulated aswould be apparent. First laser beam 340 may be divided by first opticalcoupler 322 into first target beam 312 and a first local oscillator beam342. First local oscillator beam 342 may be held for a first delayperiod at a first beam delay 344.

In some embodiments of the invention, second laser source 320 may emit asecond laser beam 346 at a second frequency. The second frequency may bemodulated at a second chirp rate different from the first chirp rate.The second frequency may be modulated electrically, mechanically,acousto-optically, or otherwise modulated. The first chirp rate and thesecond chirp rate may create a counter chirp between first laser beam340 and second laser beam 346.

In some instances, the second carrier frequency may be substantially thesame as the first carrier frequency. For example, in some embodimentsthe percentage difference between the first baseline frequency and thesecond baseline frequency is less than 0.05%. This may provide variousenhancements to laser system 310, such as, for example, minimizingdistortion due to speckle, or other enhancements. Second laser beam 346may be divided by second optical coupler 324 into a second target beam314 and a second local oscillator beam 348. Second local oscillator beam348 may be held for a second delay period at a second beam delay 350.The second delay period may be different than the first delay period.

In some embodiments, the output(s) of first laser source 318 and/orsecond laser source 320 (e.g. first laser beam 340 and/or second laserbeam 346) may be linearized using mechanisms provided in, for example,Metris USA Model MV200. Phase wandering of the output(s) of first lasersource 318 and/or second laser source 320 may be corrected usingmechanisms provided in, for instance, Metris USA Model MV200.

In some embodiments of the invention, laser radar system 310 maydetermine the range and the range rate of target 316 with an increasedaccuracy when the range of target 316 from laser radar system 310 fallswithin a set of ranges between a minimum range and a maximum range. Whenthe range of target 316 does not fall within the set of ranges, theaccuracy of laser radar system 310 may be degraded.

According to various embodiments of the invention, first beam delay 344and second beam delay 350 may be adjustable. Adjusting first beam delay344 and second beam delay 350 may enable laser radar system 310 to beadjusted to bring the set of ranges over which more accuratedeterminations may be made closer to, or further away from, laser radarsystem 310. First beam delay 344 and the second beam delay 350 may beadjusted to ensure that the range of target 316 falls within the set ofranges between the minimum range and the maximum range so that the rangeand the range rate of target 316 may be determined accurately. Firstbeam delay 344 and second beam delay 350 may be adjusted by a user, orin an automated manner.

The degradation of determinations of range and range rate when the rangeof target 316 is outside of the set of ranges may be a result of thefinite nature of the coherence length of first laser source 318 andsecond laser source 320. For example, the distance between the minimumrange and the maximum range may be a function of the coherence length.The longer the coherence length of first laser source 318 and secondlaser source 320, the greater the distance between the minimum range andthe maximum range may be. Thus, increasing the coherence length of firstlaser source 318 and second laser source 320 may enhance range and rangerate determinations by laser radar system 310 by providing the abilityto make determinations over an enhanced set of ranges.

In some embodiments of the invention, first local oscillator beam 342may be divided into a plurality of first local oscillator beams andsecond local oscillator beam 348 may be divided into a plurality ofsecond local oscillator beams. In such instances, laser radar system 310may include a plurality of beam delays that may apply delays of varyingdelay periods to the plurality of first local oscillator beams and theplurality of second local oscillator beams. This may ensure that one ofthe plurality of first local oscillator beams and one of the pluralityof second local oscillator beams may have been delayed for delay periodsthat may enable the range and range rate of the target to be determinedaccurately.

Accordingly, in some embodiments of the invention, first laser source318 and second laser source 320 may emit chirped electromagneticradiation with an enhanced coherence length. For example, first lasersource 318 and/or second laser source 320 may include system 310 asillustrated in FIG. 3 and described above.

According to various embodiments, first target beam 312 and secondtarget beam 314 may be directed and/or received from target 316 onseparate optical paths. In some embodiments, these optical paths may besimilar but distinct. In other embodiments, first target beam 312 andsecond target beam 314 may be coupled by a target optical coupler 326into a combined target beam 352 prior to emission that may be directedtoward target 316 along a common optical path. In some embodiments,combined target beam 352 (or first target beam 312 and second targetbeam 314, if directed toward target 316 separately) may be reflected bytarget 316 and may be received by laser radar system 310 along areception optical path separate from the common optical path thatdirected combined target beam 352 toward target 316. Such embodimentsmay be labeled “bistatic.” Or, combined target beam 352 may be receivedby laser radar system 310 as a reflected target beam 356 along thecommon optical path. These latter embodiments may be labeled“monostatic.” Monostatic embodiments may provide advantages over theirbistatic counterparts when operating with reciprocal optics. Inmonostatic embodiments, the common optical path may include opticalmember 328 that may provide a common port for emitting combined targetbeam 352 and receiving reflected target beam 356. Optical member 328 mayinclude an optical circulator, an optical coupler or other opticalmember as would be apparent.

In some embodiments, the common optical path may include a scanningelement 337. Scanning element 337 may include an optical element suchas, for instance, a mirror, a lens, an antenna, or other opticalelements that may be oscillated, rotated, or otherwise actuated toenable combined target beam 352 to scan target 316. In some instances,scanning element 337 may enable scanning at high speeds. In conventionalsystems, scanning elements may be a source of mirror differentialDoppler noise effects due to speckle or other optical effects that maydegrade the accuracy of these systems. However, because variousembodiments of laser radar system 310 use simultaneous measurements (orsubstantially so) to unambiguously determine range and range rate,inaccuracies otherwise induced by high speed scanning may be avoided.

In some embodiments of the invention, a target optical coupler 354 maydivide reflected target beam 356 into a first reflected target beamportion 358 and a second reflected target beam portion 360. First localoscillator optical coupler 330 may combine first local oscillator beam342 with first reflected target beam portion 358 into a first combinedtarget beam 362. Second local oscillator optical coupler 332 may combinesecond local oscillator beam 348 with second reflected target beamportion 360 into a second combined target beam 364. In some embodimentsnot shown in the drawings, where, for example first target beam 312 andsecond target beam 314 may be directed to and/or received from target316 separately, first local oscillator optical coupler 330 may combinefirst target beam 312 that is reflected with first local oscillator beam342 to create first combined target beam 362, and second target beam 314that is reflected may be combined with second local oscillator beam 348to create second combined target beam 364.

Because first local oscillator beam 342 and second local oscillator beam348 may be combined with different target beams, or different portionsof the same target beam (e.g. reflected target beam 356), first combinedtarget beam 362 and second combined target beam 364 may representoptical signals that might be present in two separate, but coincident,single laser source frequency modulated laser radar systems, just priorto final processing. For example, laser source controller 336, firstlaser source 318, first optical coupler 322, first beam delay 344, andfirst local oscillator optical coupler 330 may be viewed as a firstlaser radar section 374 that may generate first combined target beam 362separate from second combined target beam 364 that may be generated by asecond laser radar section 376. Second laser radar section 376 mayinclude laser source controller 338, second laser source 320, secondoptical coupler 324, second beam delay 350, and second local oscillatoroptical coupler 332.

In some embodiments, laser radar system 310 may include a processor 334.Processor 334 may include a detection module 366, a mixing module 368, aprocessing module 370, and/or other modules. The modules may beimplemented in hardware (including optical and detection components),software, firmware, or a combination of hardware, software, and/orfirmware. Processor 334 may receive first combined target beam 362 andsecond combined target beam 364. Based on first combined target beam 362and second combined target beam 364, processor 334 may generate therange signal and the range rate signal. Based on the range signal andthe range rate signal, the range and the range rate of target 316 may beunambiguously determined.

In some embodiments of the invention, processor 334 may determine afirst beat frequency of first combined local oscillator beam 362. Thefirst beat frequency may include a difference in frequency, attributableto a difference in path length, of first local oscillator beam 342 andthe component of reflected target beam 356 that corresponds to firsttarget beam 312 that has been reflected from target 316. Processor 334may determine a second beat frequency of second combined localoscillator beam 364. The second beat frequency may include a differencein frequency, attributable to a difference in path length, of secondlocal oscillator beam 348 and the component of reflected target beam 356that corresponds to second target beam 314 that has been reflected fromtarget 316. The first beat frequency and the second beat frequency maybe determined simultaneously (or substantially so) to cancel noiseintroduced by environmental or other effects. One or more steps may betaken to enable the first beat frequency and the second beat frequencyto be distinguished from other frequency components within firstcombined target beam 362, other frequency components within secondcombined target beam 364, and/or each other. For example, these measuresmay include using two separate chirp rates as the first chirp rate andthe second chirp rate, delaying first local oscillator beam 342 andsecond local oscillator beam 350 for different delay times at first beamdelay 344 and second beam delay 350, respectively, or other measures maybe taken.

It will be appreciated that while FIG. 3 illustrates an exemplaryembodiment of the invention implemented primarily using optical fibersand optical couplers, this embodiment is in no way intended to belimiting. Alternate embodiments within the scope of the invention existin which other optical elements such as, for example, prisms, mirrors,half-mirrors, beam splitters, dichroic films, dichroic prisms, lenses,or other optical elements may be used to direct, combine, direct, focus,diffuse, amplify, or otherwise process electromagnetic radiation.

According to various embodiments of the invention, processor 334 may mixfirst combined target beam 362 and second combined target beam 364 toproduce a mixed signal. The mixed signal may include a beat frequencysum component that may correspond to the sum of the first beat frequencyand the second beat frequency, and a beat frequency difference componentthat may correspond to the difference between the first beat frequencyand the second beat frequency. For a target having constant velocity,first laser beam 340 and second laser beam 346 beat frequencies may bedescribed as follows:

$\begin{matrix}{{{f_{1}(t)} = {\frac{4\pi \; v}{\lambda_{1}} + {2\pi \; {\gamma_{1}\left( {R - {RO}_{1}} \right)}}}},{and}} & (1) \\{{{f_{2}(t)} = {\frac{4\pi \; v}{\lambda_{2}} + {2\pi \; {\gamma_{2}\left( {R - {RO}_{2}} \right)}}}},{respectively},} & (2)\end{matrix}$

where f₁(t) represents the first beat frequency, f₂(t) represents thesecond beat frequency, λ₁ and λ₂ are the two optical wavelengths, v isthe target velocity, γ₁ and γ₂ are proportional to the respective chirprates, R is the measured range and RO₁ and RO₂ represent the rangeoffsets for the two laser radars. Now assume that λ₁=λ₂=λ. We maysubtract the equations to yield

f ₁(t)−f ₂(t)=2πR(γ₁−γ₂)−2π(γ₁RO₁−γ₂RO₂)  (3)

Rearranging (3) we obtain

$\begin{matrix}{R = {\frac{\left( {{f_{1}(t)} - {f_{2}(t)}} \right)}{2{\pi \left( {\gamma_{1} - \gamma_{2}} \right)}} + \frac{\left( {{\gamma_{1}{RO}_{1}} - {\gamma_{2}{RO}_{2}}} \right)}{\left( {\gamma_{1} - \gamma_{2}} \right)}}} & (4)\end{matrix}$

as the corrected range measurement. Similarly we may combine (1) and (2)to obtain the expression,

$\begin{matrix}{{v = {{\frac{\lambda}{4\pi}\left( \frac{{f_{1}(t)} - {\frac{\gamma_{1}}{\gamma_{2}\;}{f_{2}(t)}}}{1 - \frac{\gamma_{1}}{\gamma_{2}}} \right)} + {\frac{\lambda \; \gamma_{1}}{2}\left( \frac{{RO}_{1} - {RO}_{2}}{1 - \frac{\gamma_{1}}{\gamma_{2\;}}} \right)}}},} & (5)\end{matrix}$

which provides a measure of the target velocity.

According to various embodiments of the invention, the beat frequencysum component, described above in Equation 4, may be filtered from themixed signal to produce a range signal. From the beat frequency sumcomponent included in the range signal (e.g. f1(t)+f2(t)), adetermination of the distance from laser radar system 310 to target 316may be made. The determination based on the range signal may beunambiguous, and may not depend on either the instantaneous behavior, orthe average behavior of the Doppler frequency shift (e.g. v/λ).

In some embodiments, the beat frequency difference component, describedabove in Equation 4, may be filtered from the mixed signal to produce arange rate signal. From the beat frequency difference component includedin the range rate signal, a determination of the range rate of target316 may be unambiguously made. To determine the range rate of target316,

${f_{1}(t)} - {\frac{\gamma_{1}}{\gamma_{2}}{f_{2\;}(t)}}$

may be represented as a value proportional to a chirp rate differencebetween the first chirp rate and the second chirp rate. This may enablethe Doppler shift information to be extracted, which may represent aninstantaneous velocity (i.e., range rate) of target 316.

In some embodiments of the invention, the second chirp rate may be setto zero. In other words, second laser source 318 may emit radiation at aconstant frequency. This may enable second laser source 318 to beimplemented with a simpler design, a small footprint, a lighter weight,a decreased cost, or other enhancements that may provide advantages tothe overall system. In such embodiments, laser radar system 310 mayinclude a frequency shifting device. The frequency shifting device mayinclude an acousto-optical modulator 372, or other device.Acousto-optical modulator 372 may provide a frequency offset to secondlocal oscillator beam 348, which may enhance downstream processing. Forexample, the frequency offset may enable a stationary target beatfrequency between second local oscillator beam 348 and second reflectedtarget beam portion 360 representative of a range rate of a stationarytarget to be offset from zero so that the a direction of the target'smovement, as well as a magnitude of the rate of the movement, may bedetermined from the beat frequency. This embodiment of the invention hasthe further advantage that it may allow for continuous monitoring of thetarget range rate, uninterrupted by chirp turn-around or fly-back. Chirpturn-around or fly-back may create time intervals during which accuratemeasurements may be impossible for a chirped laser radar section. Inthese embodiments, laser radar section 376 may only determine the rangerate of target 316 while laser radar system 310 retains the ability tomeasure both range and range rate.

FIG. 4 illustrates a processor 334 according to one embodiment of theinvention. Processor 334 may mix first combined target beam 362 andsecond combined target beam 364 digitally. For example, processor 334may include a first detector 410 and a second detector 412. The firstdetector 410 may receive first combined target beam 362 and may generatea first analog signal that corresponds to first combined target beam362. The first analog signal may be converted to a first digital signalby a first converter 414. Processor 334 may include a first frequencydata module 416 that may determine a first set of frequency data thatcorresponds to one or more frequency components of the first digitalsignal. In some instances, the first digital signal may be averaged at afirst averager module 418. In such instances, the averaged first digitalsignal may then be transmitted to first frequency data module 416.

Second detector 412 may receive second combined target beam 364 and maygenerate a second analog signal that corresponds to second combinedtarget beam 364. The second analog signal may be converted to a seconddigital signal by a second converter 420. Processor 334 may include asecond frequency data module 422 that may determine a second set offrequency data that corresponds to one or more of frequency componentsof the second digital signal. In some instances, the second digitalsignal may be averaged at a second averager module 424. In suchinstances, the averaged second digital signal may then be transmitted tosecond frequency data module 422.

The first set of frequency data and the second set of frequency data maybe received by a frequency data combination module 426. Frequency datacombination module 426 may linearly combine the first set of frequencydata and the second set of frequency data, and may generate a range ratesignal and a range signal derived from the mixed frequency data.

FIG. 5 illustrates a processor 334 according to another embodiment ofthe invention. Processor 334 may include a first detector 510 and asecond detector 512 that may receive first combined target beam 362 andsecond combined target beam 364, respectively. First detector 510 andsecond detector 512 may generate a first analog signal and a secondanalog signal associated with first combined target beam 362 and secondcombined target beam 364, respectively. Processor 334 may mix firstcombined target beam 362 and second combined target beam 364electronically to generate the range signal and the range rate signal.For example, processor 334 may include a modulator 514. Modulator 514may multiply the first analog signal generated by first detector 510 andthe second analog signal generated by second detector 512 to create acombined analog signal. In such embodiments, processor 334 may include afirst filter 516 and a second filter 518 that receive the combinedanalog signal. First filter 516 may filter the combined analog signal togenerate a first filtered signal. In some instances, first filter 516may include a low-pass filter. The first filtered signal may beconverted by a first converter 520 to generate the range rate signal.Second filter 518 may filter the combined analog signal to generate asecond filtered signal. For instance, second filter 518 may include ahigh-pass filter. The second filtered signal may be converted by asecond converter 522 to generate the range signal.

FIG. 6 illustrates a processor 334 according to yet another embodimentof the invention. Processor 334 may mix first combined target beam 362and second combined target beam 364 optically to generate the rangesignal and the range rate signal. For example, processor 334 may includea detector 610 that receives first combined target beam 362 and secondcombined target beam 364 and generates a combined analog signal based onthe detection. In such embodiments, processor 334 may include a firstfilter 612 and a second filter 614 that receive the combined analogsignal. First filter 612 may filter the combined analog signal togenerate a first filtered signal. First filter 612 may include alow-pass filter. The first filtered signal may be converted by a firstconverter 616 to generate the range rate signal. Second filter 614 mayfilter the combined analog signal to generate a second filtered signal.Second filter 14 may include a high-pass filter. The second filteredsignal may be converted by a second converter 618 to generate the rangesignal.

Although the invention has been described in detail for the purpose ofillustration based on what is currently considered to be the mostpractical and preferred embodiments, it is to be understood that suchdetail is solely for that purpose and that the invention is not limitedto the disclosed embodiments, but, on the contrary, is intended to covermodifications and equivalent arrangements that are within the spirit andscope of the appended claims. For example, it is to be understood thatthe present invention contemplates that, to the extent possible, one ormore features of any embodiment can be combined with one or morefeatures of any other embodiment.

1-19. (canceled)
 20. A system for determining motion of a feature of anindividual, the system comprising: a video imaging system configured tocapture a plurality of images of a face of the individual; a lidarsystem configured to generate a range measurement and a Doppler velocitymeasurement for each of a plurality of points on the face of theindividual; and a processor configured to: determine, from the pluralityof images of the face, a lateral motion of the face in an image plane ofthe plurality of images of the face, a vertical motion of the face inthe image plane of the plurality of images of the face, and a rotationof the face in the image plane of the plurality of images, determine,from the range measurement and the Doppler velocity measurement for eachof the plurality of points on the face, a translational motion of theface in a direction of the range measurement and two rotational motionsof the face orthogonal to the direction of the range measurement, andcombine the lateral motion of the face, the vertical motion of the face,and the rotation of the face determined from the plurality of images ofthe face with the translational motion of the face and the tworotational motions of the face determined from the range measurement andthe Doppler velocity measurement for each of the plurality of points onthe face to determine the motion of the face of the individual.
 21. Thesystem of claim 20, wherein the processor is further configured toadjust a position or a motion of the feature of the individual using themotion of the face of the individual.
 22. The system of claim 21,wherein the processor is configured to adjust a position or a motion ofan eyeball of the individual using the motion of the face of theindividual.
 23. A method for determining motion of a feature of anindividual, the method comprising: capturing, via a video imagingsystem, a plurality of images of a face of the individual via a videoimaging system; generating, via a lidar system, a range measurement anda Doppler velocity measurement for each of a plurality of points on theface of the individual; determining, from the plurality of images of theface, a lateral motion of the face in an image plane of the plurality ofimages of the face, a vertical motion of the face in the image plane ofthe plurality of images of the face, and a rotation of the face in theimage plane of the plurality of images; determining, from the rangemeasurement and the Doppler velocity measurement for each of theplurality of points on the face, a translational motion of the face in adirection of the range measurement and two rotational motions of theface orthogonal the direction of the range measurement; and combiningthe lateral motion of the face, the vertical motion of the face, and therotation of the face determined from the plurality of images of the facewith the translational motion of the face and the two rotational motionsof the face determined from the range measurement and the velocitymeasurement for each of the plurality of points on the face to determinethe motion of the face of the individual.
 24. The method of claim 23,further comprising adjusting a position or a motion of the feature ofthe individual using the motion of the face of the individual.
 25. Themethod of claim 24, wherein adjusting a position or a motion of thefeature of the individual using the motion of the face of the individualcomprises adjusting a position or a motion of an eyeball of theindividual using the motion of the face of the individual.
 26. A methodfor determining motion of a feature of an individual, the methodcomprising: capturing, via a video imaging system, a plurality of imagesof the individual via a video imaging system; generating, via a lidarsystem, a range measurement and a Doppler velocity measurement for eachof a plurality of points on the individual; determining, from theplurality of images of the individual, a lateral motion of theindividual in an image plane of the plurality of images of theindividual, a vertical motion of the individual in the image plane ofthe plurality of images of the individual, and a rotation of theindividual in the image plane of the plurality of images of theindividual; determining, from the range measurement and the Dopplervelocity measurement for each of the plurality of points on theindividual, a translational motion of the individual in a direction ofthe range measurement and two rotational motions of the individualorthogonal to the direction of the range measurement; and combining thelateral motion of the individual, the vertical motion of the individual,and the rotation of the individual determined from the plurality ofimages of the individual with the translational motion of the individualand the two rotational motions of the individual determined from therange measurement and the Doppler velocity measurement for each of theplurality of points on the individual to determine the motion of theindividual.
 27. The method of claim 26, further comprising adjusting aposition or a motion of the feature of the individual using the motionof the individual.